1. Field of the Invention
The present invention relates to an optical pick-up position detector for detecting a position of an optical pick-up for use in a recording/reproducing device for an optical disk such as a compact. disk.
2. Description of the Related Art
In recent years, optical disks have been used in various technical fields as recording media capable of mass data recording, and optical disk recording/reproducing devices have been actively improved for speeding up recording/reproducing of data relative to the optical disks. FIG. 5 shows a suspension chassis structure of a compact disk player which has been generally used. In FIG. 5, numeral 1 denotes an optical pick-up for reading and writing data relative to an optical disk 6, 2 a traverse motor for driving the optical pick-up 1, 3 a lead screw, and 4 a guide shaft. The lead screw 3 has a thread which meshes with a thread of a joint portion 5 of the optical pick-up 1. The rotation of the traverse motor 2 is transmitted to the lead screw 3 via gears and then to the optical pick-up I via the joint portion 5 so that the optical pick-up 1 is moved in a radial direction, i.e. radially inward or outward, with respect to the optical disk 6.
When the optical disk 6 is inserted, the compact disk player once moves the optical pick-up 1 to the radially innermost position of he optical disk 6 for detecting a position of the optical pick-up 1. When the optical pick-up 1 reaches the innermost position, the optical pick-up 1 pushes an inner switch 7 provided in the suspension chassis structure so that the switch 7 is closed to the ON state. In response to the closing operation of the switch 7, the traverse motor 2 starts reverse rotation so that the optical pick-up 1 starts to move radially outward.
A series of the foregoing operations are controlled by an optical pick-up position detection circuit of the compact disk player. FIG. 6 shows a structure of the conventional position detection circuit, while FIG. 7 shows a timing chart for explaining an operation of the conventional position detection circuit. As shown in FIG. 6, the conventional position detection circuit comprises a suspension chassis section 8, a relay connector section 9 and a main substrate section 10. While the switch 7 is open (OFF state), a high-level signal S5 of a given voltage is inputted into a microcomputer 13 via a resistor 12 from a power supply 11 for the microcomputer 13. In response to the signal S5, the microcomputer 13 outputs a signal S4 to a driver IC 14 so that the driver IC 14 gives a high-level signal S1 to a relay connector terminal P1 and a low-level signal S2 to a relay connector terminal P2. As a result, the traverse motor 2 is rotated to move the optical pick-up 1 radially inward. In FIG. 6, numeral 15 denotes a power supply for the driver IC 14.
When the optical pick-up 1 reaches the radially innermost position to push and close the switch 7 to the ON state, the voltage of the power supply 11 reaches the ground 17 via relay connector terminals P3 and P4. Thus, signals S3 and S6 as well as a signal S5 which is inputted into the microcomputer 13 become approximately OV, i.e. a low level. In response to the low-level signal S5, the microcomputer 13 outputs a signal S4 to the driver IC 14 so that the driver IC 14 gives a low-level signal S1 to the terminal P1 and a high-level signal S2 to the terminal P2. As a result, the traverse motor 2 starts reverse rotation to move the optical pick-up 1 radially outward.
In the foregoing conventional position detection circuit, however, the control implemented by the microcomputer 13 according to the state of the switch 7 is independent of the polarity of the voltage applied to the traverse motor 2, and thus, four relay connector terminals are required. Further, although the information about the state (ON/OFF) of the switch 7 is fed to the microcomputer 13, no information about the polarity of the voltage applied to the traverse motor 2 is fed back to the microcomputer 13.